Re: pass rules for one alert

[TheEagleSociety () netscape net (Night-Stalker)]

Hello John,

the Payload, that snort logs looks like this:

  length = 131
  LIST..PASV..CDW //directory1/directory2..LIST..PASV..
  CWD //directory3/directory4..LIST..PASV..

As I can see, it must be hourly cron-job from host1 to host2 via FTP. Every hour, I get 5 false positives of this 
alert. Only between these hosts. My pass-rule, I wrote below doesn't work, or it works but also triggers the 
alert-rule. As I wrote, I only want to ignore this false positive between these hosts and I dont't want to comment out 
the complete alert-rule to ignore all these alerts. I also don't want to write a pass-rule to ignore the complete 
FTP-Transfers between these hosts.
Can anybody help me out?

Thanks

Addy


John Sage <jsage () finchhaven com> wrote:
> > Addy:
> > **-- snip --**
> >
> > pass tcp <source-ip> any -> <dest-ip> 21 (msg:"FTP command overflow
> > attempt"; flags:A+; dsize:>100; reference:bugtraq,4638;
> > classtype:protocol-command-decode; sid:1748; rev:3;)
>
> This is looking at a packet payload size > 100; this is not specific
> enough?
>
> What *would* make it specific enough? See below...
>
> > I don't want to ignore all FTP-Data between these hosts, only the
> > FTP-Data that triggers this alert (thats means the pass-rule:
> > pass tcp <source-ip> any -> <dest-ip> 21
> > isn't precise enough. And ignores all FTP-Data.)
> >
> > Is it possible to ignore exactly the FTP-Data between these Hosts,
> > that triggers that alert. I want the other FTP-Data between these
> > Hosts being scanned for other FTP-Exploits except the "FTP command
> > overflow attempt".
>
> In a word, yes, but if you want help from anyone on this list you'll
> have to tell *us* what "..exactly the FTP-Data between these Hosts.."
> is, because until we know, no one can help you...
>
>
> - John
> -- 
> "In those days, you could not buy a $2000 200MHz Pentium server."


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